Catchment Weir De-silting Trial
The Water Supply Headworks contains a number of weirs that are used to divert water from catchment streams to storage reservoirs. Over time these weirs experience a buildup of silt and sediment which needs to be removed. Currently this sediment is removed by either draining the weir during low flow periods or by bypass pumping around the weir. The wet sediment is then removed using earth moving equipment such as excavators and trucks.
In June/July this year the Water Civil Maintenance Team trialed an alternative process for de-silt the East Armstrong Weir within the Armstrong Catchment. The trial involved the deployment of a floating dredge and pumping system. The floating dredge sucks up the silt and pumps it to a geotextile dewatering tube. The geotextile dewatering tube (pictured below) acts like a filter bag and capture the silt and sediment while letting the water pass through where it runs back into the weir.
Testing of the return water has found it to be cleaner than the water in the weir. The sediment in the geotextile dewatering tube is then allowed to naturally fully dry before being disposed of.
This new process was found to have great potential as it does not require the weir to be drained or bypass pumped.. It also negates the need to excavate and cart wet silt which significantly reduces material handling costs.